The manufacture of integrated-circuit devices such as, e.g., semiconductor memory and logic chips involves numerous processing steps including ion implantation, deposition of dielectric and conductor layers on a wafer substrate, and photolithographic patterning and etching. More particularly with respect to the deposition of conductor layers on a dielectric, such layers may be formed, e.g., by (physical) sputtering or by chemical vapor deposition (CVD), the former being in current use for aluminum, and the latter for tungsten. In the following, attention is directed primarily to the formation, by chemical vapor deposition, of a metallization layer on a dielectric.
One difficulty encountered in this connection arises from typically unsatisfactory adhesion, e.g., of CVD-tungsten to the dielectric, making it advisable, prior to metal deposition, to form an auxiliary, adhesion-enhancing "glue" layer. Since such glue layer is typically deposited by sputtering onto the face of a wafer while the wafer's edge is held by chips, the wafer back side, the wafer edge, and small areas of the wafer face underlying the clips ("clip marks") remain essentially as uncoated dielectric. As a result, subsequently deposited CVD-tungsten material tends to flake off from such uncoated areas in the coarse of further processing, thereby contaminating processing apparatus and interfering with desired processing.
The invention described below is motivated by the desired to prevent metal flake-off and attendant contamination and interference.